The present invention relates to machine tools in general, especially to grinding machines, and more particularly to improvements in machine tools of the type wherein the material removing tool or tools are partially surrounded by a protective hood which reduces the likelihood of injury as well as the likelihood of contamination of the surrounding area by fragments of removed material and/or sprays of liquid coolant or the like.
A surface grinding machine normally comprises a frame, at least one rotary spindle which is mounted in the frame and carries one or more grinding wheels, a work holder, combined guide and drive means for effecting a relative movement between the grinding wheel or wheels on the spindle and the workpiece on the holder so as to treat selected portions of or the entire workpiece, and a protective hood or shroud which at least partially surrounds the grinding wheel(s) and can be provided with means for supplying one or more sprays or streams of coolant, at least into the zone of contact between the grinding wheel(s) and the workpiece.
The protective hood or shroud should be placed as close to the adjacent surface of the workpiece as possible for obvious reasons. On the other hand, the hood should not come into actual contact with the workpiece. Such optimum positioning of the hood presents no problems when the surface to be treated by one or more grinding wheels is flat, i.e., the open side of the hood is then placed into immediate proximity of the path of movement of the surface which requires treatment so as to reduce to a minimum the likelihood of splashing of coolant and/or spraying of removed material as well as to protect the attendants from injury and/or discomfort. However, if the workpiece has an uneven (e.g., convex, concave or undulate) surface which is to be treated and/or formed by the grinding wheel(s), the distance between the hood and the workpiece must be selected with a view to ensure that the topmost portion of the surface also does not actually contact the hood while the workpiece is caused to move relative to the hood and grinding wheel(s) and/or vice versa. In other words, it can happen that the hood is located at a considerable distance from the workpiece during certain stages of a grinding operation upon a workpiece having a highly uneven profile with pronounced hills and valleys so that the protective or shielding effect of the hood is negligible or zero. Moreover, and as mentioned above, it is customary to install in the hood one or more nozzles or other devices which direct a liquid coolant against the region of contact between the workpiece and the grinding wheel(s). The orientation of such nozzle or nozzles is satisfactory as long as the grinding machine is to treat flat surfaces of workpieces. However, if the surfaces to be treated exhibit pronounced hills and valleys, so that the hood must be installed at a considerable distance from the path of movement of the lowermost or deepmost portions of workpieces past the grinding wheel and/or vice versa, the nozzle or nozzles discharge streams of coolant in directions other than toward the region of contact between the workpiece and one or more grinding wheels. Absence of adequate cooling of the region of contact between the grinding wheel(s) and the workpiece can affect the quality of the grinding operation and entail damage to the workpiece and/or grinding wheels as a result of insufficient lubrication and/or overheating.